Pacific Interannual and Multidecadal Variability Recorded in δ¹⁸O of South American Summer Monsoon Precipitation

Author(s)

Orrison, R. ; Vuille, M. ; Rodrigues, J. C. ; Strikis, N. M. ; Cruz, F. ; Rodriguez-Caton, M. ; Andreu-Hayles, L.

• Document type: Journal article
• Source: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES; v. 129, n. 17, p. 19-pg., 2024-09-16.

Abstract

The South American summer monsoon (SASM) generates important hydroclimatic impacts in (sub-)tropical South America and isotopic tracers recorded in paleoclimatic archives allow for assessing its long-term response to Pacific variability prior to modern observations. Stable oxygen isotopes in precipitation integrate hydroclimatic changes during the SASM mature phase from December to February (DJF) in response to the Interdecadal Pacific Oscillation (IPO) and El Ni & ntilde;o-Southern Oscillation (ENSO), respectively. Here, results from the isotope-enabled Community Atmosphere Model v.5 are compared with highly resolved and precisely dated isotopic records from speleothems, tree rings, lake and ice cores during the industrial era (1880-2000 CE) and validated against observations from the International Atomic Energy Agency (IAEA) network. Pacific sea surface temperatures (SSTs) are coupled to the isotopic composition of SASM precipitation through perturbations in the Walker circulation associated with low- (IPO) and high-frequency (ENSO) variability, impacting convective activity over tropical South America and the tropical Atlantic. Changes in convection over this monsoon entrance region ultimately control the downstream oxygen isotopic composition of precipitation recorded in paleoclimate archives. Overall, model results, paleoclimate records and IAEA data agree on the isotopic response to Pacific SST forcing. These results highlight the potential for long isotopic paleoclimate records to reconstruct Pacific climate variability on both high- and low-frequency timescales. Furthermore, the isolation of the IPO signal in a diverse set of isotopic archives invites the reinterpretation of other paleoclimate proxies for identifying this historically overlooked forcing. (AU)

• FAPESP's process: 17/50085-3 - PIRE: climate research education in the Americas using tree-ring speleothem examples (PIRE-CREATE)
• Grantee: Francisco William da Cruz Junior
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 19/02791-1 - Study on the variability of extreme rain events based on geochemistry high resolution analysis (d18O e d13C and trace elements) in speleothems
• Grantee: Julio Cauhy Rodrigues
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 22/08359-7 - Interhemispheric monsoon precipitation patterns under different warming backgrounds in the past 140 KA and the anthropocene epoch
• Grantee: Francisco William da Cruz Junior
• Support Opportunities: Research Program on Global Climate Change - Regular Grants